Well, with the cave come out i have a strategy to get free gold every month.
For those who can spend real money into DS , i recommend buying it right away. You spend 100$ and get 5 caves. Every month you get back the gold to re-buy new caves and 172x5= 860 free gold per month to spend.
With this cave you spend the money once and can get free gold every month continuosly. Still dont get why would you think its not worth it or spend 10$ is cheeper ??